small motor drags more current?? advice needed

[kenkaiser]

Hey there, Could someone take a look at this set up and see what you think.
(http://xoomee.com/help.htm)
I can get really good peformance out of each of these motor/prop sets using the battery shown below (7aaa cell NiMH pack) EXCEPT for the tiny motor/prop set shown in the middle. The tiniest motor drags the battery down to the point where the ESC will cut power to the motor conserving it for the controls even on a fresh charge. On the larger motors and props, it runs just fine with plenty of power for about 10 minutes. The motor is from a toy free flight plane you can get at Harbor Freight Tools and actually flies very well. I want to use it, either direct drive as shown, or geared down for a lightweight RC plane I am designing. However, even with the prop removed, it sucks down the juice in the battery and bogs down. I am sure this is a basic electronics thing, but I can't figure it out, anybody know? Let me know if you need more info on the equipment or my intended application.

I am building a DH53 Hummingbird, I will post the plans as soon as I can.

Thanks in advance, Kenny

[Dave Robelen]

Hello Kenny.
There are a couple of possibilities. The small motor may well be intended for fewer cells and is drawing excesive current on the present battery. Something may be binding (does it spin smootlhy) or the brushes are shorting inside the housing. Hard to say really without actually looking it over.
Regards, Dave Robelen

[kenkaiser]

A single 2/3AAA battery was the original energy source for that motor.

The motor seems very strong like some electric motors, you can feel the magnetic resistance. Just like those Pico motors, you can feel that magnetic pull when you slowly turn the prop, it springs to as it goes around.

I can hook the motor directly to a 3 cell nicad (cordless phone) battery which I use for my RC sailplane and it runs great. But 3 cells won't work with the RC, so I hooked it up to a 5 cell AAA on the RC and it did work, but it got super hot in just a few seconds.

I was thinking that a motor like this could be geared down and used on a smaller RC airplane, but it is not shaping up that way.

[Dave Robelen]

Hello Kenny,
If the motor is wound to run on a very small number of cells, it is almostcertainly going to draw very high current on a larger pack. Also, the life of the motor would be mighty short.
Regards, Dave Robelen

[kenkaiser]

Thanks for the advice, you said it correctly, the life span of the motor was short. It completely died last night during my experiments with the different batteries. I guess when I am buying a motor I should look for one rated at least 6 volts to be able to handle a multi-cell battery pack.

Kenny

[2NG]

Their all right:D BATTERY



Volts + mAh= power
- Volts + mAh= - power (Think) hummmm


2NG


:cool: